To punch holes in metal parts, each punch is generally mounted in a retainer which is in turn mounted on a die shoe located in a press. Typically, the punch retainer comprises a steel body having a through bore in which the punch is removably secured. Within the body of the punch retainer there is formed a circular bore which is perpendicular to the top face of the body. A circular cylindrical shank having a punch is releasibly retained in the bore by means of a ball and spring. For punch retention, the shank of the punch is provided in the outside thereof with a groove forming an arcuate recessed surface. The recessed surface is positioned opposite the opening from the lower end of the bore. The ball engages an inwardly inclined face portion of the punch shank, referred to as a ball seat. The preferred recess shape of the ball seat resembles a teardrop. The ball is biased into engagement with the ball seat by the compression spring which loads the ball to secure the punch in place.
Currently, the ball seat in the shank of the punch is formed manually by precisely drilling the groove or recess into the shank. This can be a time consuming and labor intensive process. Therefore, it is desirable to automate the method for grinding the recess into the punch or other cylindrical workpieces.